The present invention relates generally to gas turbine power generation.
On hot days, water fog injection at the inlet of a gas turbine is often practiced to cool the air with significant enhancements of power and efficiency. However, the cooling is only moderately effective in increasing efficiency at part load where mobile and marine power systems must generally operate. Power generation and propulsion installations involving gas turbine engines on-board naval marine vessels operating under part-load conditions cannot maintain low fuel consumption when fuel throttle flow control is the only available facility for such purpose. Fuel control only for such purpose is ineffective because airflow decreases more slowly than fuel flow as power is reduced so that the combustion temperature falls, which results in a high fuel consumption rate and lower efficiency. Injection of waterfog increases the power per unit of airflow so that less air is required for the same power. A large airflow through the gas turbine engine for power generation necessitates large inlet and exhaust ducting air stacks mounted high on the ship superstructure. Volumetrically massive and tall air stacks create poor sea keeping conditions on high seas and the increased radar cross-section contributes to naval ship vulnerability and to depletion of available deck space for weapons systems. It is therefore one objective of the present invention is to provide a gas turbine engine, which enhances the ratio of power to airflow therethrough under all loading conditions. Another objective is to increase overall efficiency of the gas turbine engine and reduce its fuel consumption, especially under partial loading conditions thereby increasing operational range. Also, improvement in operational and naval tactical capabilities of a naval ship and a reduction in its operational fuel costs are to be thereby achieved by the present invention.
In accordance with the present invention, the temperature of air required to generate power through a gas turbine engine is reduced by evaporatively cooling the compressor inlet air by water-fog injection of droplets through available nozzles at the compressor inlet. The size of the droplets and the ratio of water to the air is limited to a degree that will not cause degradation in the life and capability of the engine. Variable-area turbine nozzles control the airflow to maintain the design fuel-air ratio. A fuel valve controls the supply of fuel to assist in maintaining such fuel-air ratio and to achieve an optimum turbine-inlet temperature for low fuel consumption. The water-fog injector has water spray nozzles connected through control valves to a water tank and pump. Water droplets are introduced by ducting into the inlet. Airflow control to maintain maximum efficiency is accommodated by angular adjustment of stator blades within the sealed chamber of the gas turbine engine, by means of gearing externally mounted thereon to variably limit air flow in combination with control over the air inflow temperature during water-fog injection.